During the high-speed centrifugation of plateletrich plasma, massive aggregates are formed. Prostaglandin E.sub.1 (PGE.sub.1) is one of the most potent inhibitors of platelet aggregation known. The use of PGE.sub.1 in improving the preparation of human platelet concentrates from plasma rich in platelets and from whole blood is described by Shio et al., Science, 175: 536, 1972. Shio et al. found that the addition of PGE.sub.1 at a concentration of 10.sup.-8 to 10.sup.-7 molar prevented the clumping (aggregation) of platelets in whole blood, platelet rich plasma and platelet concentrates.
The use of PGE.sub.1 in preventing clumping of platelets in stored whole blood and platelet concentrates either at room temperature or in the cold and with a variety of anticoagulants is described by Becker et al., Science, 175: 538, 1972.
The addition of PGE.sub.1 at a concentration of 2.2.times.10.sup.-8 M to whole blood does not impair the effectiveness of fresh platelet concentrates and significantly improves platelet recovery in vitro according to Valeri et al., Science, 175: 539, 1972.